Sustained operation igniter for ram-jet missiles



March 13, 1962 D. A. WASHBURN SUSTAINED OPERATION IGNITER FOR RAM-JET MrssILEs Filed Aug. 19, 1949 F IG. l

FIG.4

United States Patent Office 3,024,607 Patented Mar. 13, 1962 3,024,607 SUSTAINED OPERATION IGNlTER FOR RAM-JET MISSILES David A. Washburn, Silver Spring, Md., assignor to the United States of America as represented by the Secreta of the Navy ry Filed Aug. 19, 1949, Ser. No. 111,316

1 Claim. (Cl. S0-39.71)

The present invention relates in general to guided missiles yand more particularly Ito `an improved igmter for ram-jet missiles.

ln carrying out tests of ram-jet guided missiles, 1t has been found necessary to employ pilot igniters to maintain burning in the combustion chambers of missiles under test. Igniters heretofore in use in burner tests in the laboratory, have included gas flames, pyrotechnic flares, `and the like. In flight testing missiles, the pyrotechnic flare has been the only suitable ignition means, because the igniters of the other types mentioned require separate supplies of fuel and/or power, which it 1s 1mpracticable to carry in an actual missile.

Pyrotechnic ilares, however, burn for relatively short times and, as guided missiles have been improved, it has been demonstrated that improvements in the flares, with a view of extend-ing their burning time, have not kept pace with improved operation and the lengthened flight time of the missiles. Consequently, a condltion has been reached in which the operation of missiles is seriously affected by the burning time (life span) of the liares used for ignition. Further extension of flight time and range of a guided missile therefore depends upon the development and utilization of a new long-burning igniter of such design that it @will operate as long as any fuel remains for the missiles ram-jet engine.

`One of the principal objects of the present invention, therefore, is to provide an igniter for a ram-jet missile which will `function for `as long a time as the missile is in powered flight.

Another object of the invention is to provide `an igniter which does not require an auxiliary fuel supply.

A further object of the invention resides in the provision of an igniter for the purpose set forth hereinabove, which will be simple in construction and efficient in operation.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

FIG. l is an axial section of a portion of a ram-jet burner rfitted with the improved -igniter of the present invention, said igniter being shown partly in section and partly in side elevation;

FIG. 2 is an enlarged detail axial sectional view showing particularly the internal construction of the igniter;

FIG. 3 is an end view of the igniter, as seen from its discharge end and on :a still larger scale; and

1FIG. 4 is a correspondingly enlarged sectional view in the plane 4--4 of FIG. 2.

Referring now to the drawings in detail, a portion of the outer shell of a guided missile is shown at `10. This shell is a heavy-walled metal tube and its bore forms a central duct or combustion chamber 11, fitted at its forward, or upstream, end with a diffuser 12 of substantially frusto-conical shape. The air vfor combustion enters the forward end of the missile and passes downstream through the `diffuser 12 and chamber 11.

The igniter of the present invention is shown as a whole at 13 and includes a cylindrical sleeve 14, open at its downstream end and formed with circumferentially spaced ports 15, `arranged in longitudinal rows. The

sleeve 14 is supported axially in the chamber 11 by a fuel feed pipe 16 in turn supported by a tubular strut 17 and is additionally supported from the shell 10, by radial struts 22. More specifically, the upstream end of said sleeve 14 terminates in a frusto-conical neck 18, and said neck is secured to the downstream end of the pipe 16, the upstream end of said pipe being secured to said stmt 17. As best seen in FIG. 1, t-he bore of the strut 17 is closed at one end but provides a passage for fuel `from the space surrounding the diffuser 12 through the pipe 16 into the sleeve 14. Said strut is rig-idly secured to the mid-portion of the diffuser 12.

As best seen in FIG. 2, the sleeve 14 has, near its upstream end, two oppositely presented fuel discharge nozzles 19, and within the sleeve, between the nozzles and the nearest of the ports 15, there is a partition or wall 20. The wall 20 and neck 18 cooperate to define an 4air-fuel mixing manifold 21.

Supported axially within the sleeve 14, medially of its length and downstream from the wall 20, by struts 9,- is a pyrotechnic flare 23, for initiating operation of the igniter. The flare 23 may be ignited by an electrically operated squib, not shown, or by any other suitable means.

A flame sustaining igniter unit is shown at 2-5 and is mounted `axially within the sleeve 14 near its rear, or downstream, end. The igniter unit 25 consists of a pipe 33 having an end portion 26 mounted axially o-n the wall 20 and in communication with the manifold 21. From the end portion 26 the pipe is bent to form an intermediate portion 27, extending about the flare 23, said portion 27 terminating at its rear, or downstream, end in -a helical vaporizing coil 28.

The pipe 33 is bent back and extends through the inside of the helix as shown at 29, then has :a U-bend at 30 and terminates in a burner nozzle 31. This has a smal-l 4aperture 32 directed downstream, as shown in FIG. 3, within the nozzle 31.

The operation of the igniter will be clear from its structure, but for convenience may be summarized briefly as fol-lows:

When the ram-jet burning is to be established, fuel is supplied from the fuel s-torage container of the ramjet to the bore of tubular strut 17, whence most of it ows through pipe 16 to the manfold 21 whence it issues through the nozzles 19. A little of the fuel flows through the pipe 33, entering it at 26, and passing through portions 27, 28, 29 and 30 thereof, until it is discharged through the opening 32 of nozzle 3-1.

Meanwhile the flare 23 has been ignited, and produces heat 'and fiame within the sleeve 14. This heats the coil 28 suficiently to vaporize the fuel therein, which thereupon issues as a gas from nozzle 31, and is ignited by the llame of the flare 23. Thus a gas llame is produced at the said nozzle, and continues to heat the coil 28, to maintain the gas supply to said nozzle, that is, the nozzle and coil constitute a regenerative burner.

In the space surrounding the sleeve 14 there is a combustible fuel-air mixture, produced from the fuel discharged from the nozzles 19` `and the air stream owing through the ram-jet. This mixture will be ignited initially by the llame of the flare, and its continuing combustion will be assured by re-ignition by the burning gas from igniter nozzle 31, should it become extinguished. Occasionally during the flight of an aerial missile, combustion of the fuel-air mixture is lost or extinguished due to intense pressure fluctuations in the combustion chamber 11, and, in addition, the ame `at the igniter nozzle 3.1 is extinguished. However, the vaporizer arrangement with the igniter nozzle 31 is so designed to have self-igniting characteristics which are due to the fact that the Vaporizer coils 28 will still be suiciently hot to continue to vaporize the liquid fuel contained therein. This fuel will then issue as a gas jet from igniter nozzle 31, as previously described. The issuing jet will then re-ignite due to the auto-ignition feature of the vaporizer arrangement. Upon re-ignition of the pilot iiame, the air-fuel mixture in the combustion chamber 11 will be re-ignited. The sleeve 14 acts as a protecting shield for the ame of the igniter, preventing it from being blown out, and at the same time the holes 15 in said sleeve permit free access of the surrounding fuel-air mixture for re-ignition purposes, and free access of the air required by the igniter flame itself.

Obviously many modifications `and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practised otherwise than as specifically described.

What is claimed is:

In an aerial missile of the ram-jet type having a body in the form of an elongated tubular duct, a diffuser and a combustor in said duct; in combination, an igniter for maintaining the burning of a combustible mixture entering said duct and passing through said combustor, said igniter comprising a conduit for liquid fuel, a manifold on the conduit and having fuel outlets directed substantially normally to the axis of the conduit, a second conduit for liquid fuel having its inlet end connected to said manifold and extending substantially the same direction as said rst conduit, said second conduit having a burner nozzle at its outlet end, said nozzle being located so that the flame thereof will heat the second conduit to vaporize liquid fuel flowing therethrough, a perforated casing enclosing said second conduit and providing communication with the fuel air mixture, and a pyrotechnic are for initially bringing said second conduit up to fuel vaporizing tempera-ture.

References Cited in the file of this patent UNITED STATES PATENTS 798,359 Miner Aug. 29, 1905 1,405,482 Bostedo Feb. 7, 1922 1,839,880 Hyatt Jan. 5, 1932 2,473,192 Blackwell June 14, 1949 2,540,594 Price Feb. 6, 1951 FOREIGN PATENTS 63,081 Austria Jan. 26, 1914 

